Diversity in Drought Traits among Commercial Southeastern US Peanut Cultivars

Commercial peanut cultivars in the USA are often grown under soil and environmental conditions resulting in intermittent periods of water deficit. Two plant traits have been identified that result in conservative use of water and allow sustained growth during drought: (1) restricted transpiration rate under high atmospheric vapor pressure deficit (VPD) and (2) earlier closure of stomata in the soil-drying cycle resulting in decreased daily transpiration rate. The objective of this study was to investigate whether there was diversity in these two putative traits for drought resistance among nine US commercial peanut cultivars. When the response to VPD was measured at an average temperature of 32∘C, eight of the nine cultivars expressed a restricted transpiration rate at high VPD. However, at 24∘C none of the cultivars exhibited a restriction of transpiration rate at high VPD. No differences were found among the nine cultivars in their response to soil drying

Transpiration Response of Cotton to Vapor Pressure Deficit and Its Relationship With Stomatal Traits

Many studies have demonstrated that the cotton in warm environments is vulnerable to water-limitations thus reducing the yield. A number of plant traits have been recommended to ameliorate the effects of water deficits on plant growth and yield. Limitation on maximum transpiration rate (TR) under high vapor pressure deficit (VPD), usually occurs during midday, is often considered as a water conservation trait. The genotypes with this trait are desirable in high VPD environments where water deficits commonly develop in the later part of the growing season. Our objective of the study was to find the genotypic variation for the trait limited TR under high VPD and also to study leaf temperature, water potential, photosynthesis, and stomatal conductance responses. Also, our objective was also to study the structural changes in the stomatal traits when exposed to long term high VPD conditions and involvement in such responses. In the present study, 17 cotton genotypes were studied for their (TR) response to various VPD environments under well irrigated conditions. Out of 17, eight genotypes limited TR after approximately 2 kPa VPD and rest of them increased their TR with increased VPD. Five selected genotypes with different TR response to increasing VPD were further studied for gas exchange and stomatal properties. All genotypes, irrespective of exhibiting limited TR at high VPD, reduced stomatal conductance, photosynthesis and water potential at high VPD of 3.3 kPa. The genotypes with limited TR modified their stomatal traits mostly on the adaxial surface with frequent and small stomata under high VPD. The genotypes with limited TR also exhibited an increase in epidermal cell expansion and stomatal index at contrasting VPD gradients to effectively balance the liquid and vapor phase conductance to limit TR at high VPD

Genotypic variability among peanut (Arachis hypogea L.) in sensitivity of nitrogen fixation to soil drying

Peanuts (Arachis hypogea L.) are often grown on sandy soils and drought stress can be a major limitation on yield. In particular, loss in nitrogen fixation activity associated with soil drying might be limiting due to the need for high nitrogen amounts in both vegetative tissues and seeds of peanut. This study examined the response of nitrogen fixation of intact plants of seventeen peanut genotypes when subjected to soil drying in pots over approximately a 2-wk period. A large range in the sensitivity of nitrogen fixation to soil drying was observed among the seventeen genotypes. Genotype ICGV86015, in particular, was found to have nitrogen fixation that was especially tolerant of soil drying. Significant positive (P<0.0001) correlation was found between the soil water content at which nitrogen fixation began decreasing and the amino acid concentration in the leaves of severely stressed plants

Genotypic variation in peanut for transpiration response to vapor pressure deficit

Conservation of soil water resulting from decreases in stomata conductance under atmospheric high vapor pressure defi cit (VPD) conditions is a possible approach for enhanced tolerance of water defi cit by crops. Water defi cit is usually a concern in peanut (Arachis hypogea L.) since it is frequently grown on sandy soils with low water-holding capacity. Seventeen peanut genotypes were studied to determine the response of their transpiration rates (TR) to VPD. The results of this study demonstrated variation among peanut genotypes with nine genotypes exhibiting a breakpoint in their VPD response at about 2.2 kPa, above which there was little or no further increase in TR. Therefore, these genotypes with a breakpoint have the possibility of soil water conservation when VPD exceeded 2.2 kPa. The remaining eight genotypes had a linear response in TR over the whole range of tested VPD. Also, the 17 genotypes could be separated into groups with differing rates of increasing TR at low VPD. The change in TR with increasing VPD may be important in determining the rate at which soil water is used under fi eld conditions

Variation in Transpiration Efficiency and Related Traits in a Groundnut Mapping Population.

Transpiration efficiency (TE) was evaluated in groundnut genotypes JUG 26, ICGS 76, CSMG 84-1, ICGS 44, ICGV 86031, TAG 24 and ICG 2773 using the dry-down method. Pot-grown plants were irrigated to 90% field capacity then subjected to drought stress (i.e. irrigating plants with 70% of the water lost the day before the onset of drought stress) at 28 days after sowing (DAS). Significant variation among the genotypes for TE was evident, with TAG 24 and ICGV 86031 showing the lowest and highest values of TE, respectively. The soil water content where transpiration began to decline relative to the control varied among the genotypes, and these threshold values were negatively correlated to TE. In another dry-down experiment, 318 F8 recombinant inbred lines (RILs) obtained from a cross between ICGV 86031 and TAG 24 were also characterized, along with their parents, for TE. Substantial variation was observed among the RILs for transpiration, TE and specific leaf area (SLA) before and after the imposition of drought stress, and for SPAD chlorophyll meter readings (SCMR) before, during and at the end of drought stress. ICGV 86031 recorded greater TE and SCMA, and lower SLA than TAG 24. The analysis of TE values for the RILs revealed that the trait segregated transgressively and was governed by polygenes. The heritability value was highest for SLA, followed by SCMR. The heritability values were low for TE and transpiration. SLA and SCMR can be useful as alternative indices when the direct biomass-based evaluation of TE is not possible

Food, Nutrition and Agrobiodiversity Under Global Climate Change

Available evidence and predictions suggest overall negative effects on agricultural production as a result of climate change, especially when more food is required by a growing population. Information on the effects of global warming on pests and pathogens affecting agricultural crops is limited, though crop–pest models could offer means to predict changes in pest dynamics, and help design sound plant health management practices. Host-plant resistance should continue to receive high priority as global warming may favor emergence of new pest epidemics. There is increased risk, due to climate change, to food and feed contaminated by mycotoxin-producing fungi. Mycotoxin biosynthesis gene-specific microarray is being used to identify food-born fungi and associated mycotoxins, and investigate the influence of environmental parameters and their interactions for control of mycotoxin in food crops. Some crop wild relatives are threatened plant species and efforts should be made for their in situ conservation to ensure evolution of new variants, which may contribute to addressing new challenges to agricultural production. There should be more emphasis on germplasm enhancement to develop intermediate products with specific characteristics to support plant breeding. Abiotic stress response is routinely dissected to component physiological traits. Use of transgene(s) has led to the development of transgenic events, which could provide enhanced adaptation to abiotic stresses that are exacerbated by climate change. Global warming is also associated with declining nutritional quality of food crops. Micronutrient-dense cultivars have been released in selected areas of the developing world, while various nutritionally enhanced lines are in the release pipeline. The high-throughput phenomic platforms are allowing researchers to accurately measure plant growth and development, analyze nutritional traits, and assess response to stresses on large sets of individuals. Analogs for tomorrow’s agriculture offer a virtual natural laboratory to innovate and test technological options to develop climate resilience production systems. Increased use of agrobiodiversity is crucial to coping with adverse impacts of global warming on food and feed production and quality. No one solution will suffice to adapt to climate change and its variability. Suits of technological innovations, including climate-resilient crop cultivars, will be needed to feed 9 billion people who will be living in the Earth by the middle of the twenty-first century

Blended Multi-Modal Deep ConvNet Features for Diabetic Retinopathy Severity Prediction

Diabetic Retinopathy (DR) is one of the major causes of visual impairment and blindness across the world. It is usually found in patients who suffer from diabetes for a long period. The major focus of this work is to derive optimal representation of retinal images that further helps to improve the performance of DR recognition models. To extract optimal representation, features extracted from multiple pre-trained ConvNet models are blended using proposed multi-modal fusion module. These final representations are used to train a Deep Neural Network (DNN) used for DR identification and severity level prediction. As each ConvNet extracts different features, fusing them using 1D pooling and cross pooling leads to better representation than using features extracted from a single ConvNet. Experimental studies on benchmark Kaggle APTOS 2019 contest dataset reveals that the model trained on proposed blended feature representations is superior to the existing methods. In addition, we notice that cross average pooling based fusion of features from Xception and VGG16 is the most appropriate for DR recognition. With the proposed model, we achieve an accuracy of 97.41%, and a kappa statistic of 94.82 for DR identification and an accuracy of 81.7% and a kappa statistic of 71.1% for severity level prediction. Another interesting observation is that DNN with dropout at input layer converges more quickly when trained using blended features, compared to the same model trained using uni-modal deep features

Cotton Genotypic Variability for Transpiration Decrease with Progressive Soil Drying

Drought is a major abiotic stress factor limiting cotton yield. It is important to identify the genotypes that can conserve water under drought stress conditions and improve yield. The objective of the current study was to evaluate cotton genotypes for water conservation traits, i.e., high FTSW (Fraction of Transpirable Soil Water) threshold for transpiration. Plants utilize water slowly by declining transpiration at high FTSW and conserving soil water, which can be used by the plant later in the growing season to improve yield. Fifteen cotton varieties were selected based on their differences in transpiration response to elevated vapor pressure deficit (VPD) to study drought responses. Two pot experiments were carried out in the greenhouse to determine the FTSW threshold for the transpiration rate as the soil dried. A significant variation (p &lt; 0.01) in the FTSW threshold values for transpiration decline was observed, ranging from 0.35 to 0.60 among cotton cultivars. Genotypes with high FTSW thresholds also displayed low transpiration under well-watered conditions. Further studies with four selected genotype contrasts in FTSW threshold values for transpiration showed differences (p &lt; 0.05 to 0.001) in gas exchange parameters and water potentials. This study demonstrated that there are alternate traits among the cotton genotypes for enhancing soil water conservation to improve yield under water-limited conditions